This invention relates to solvent extraction of one or more components from an aqueous solution or mixture.
Solvent extraction is a well-established technology for selectively removing or extracting one or more components from a solution. It can be used to remove a valuable component from contaminants or remove contaminants from a valuable component. For example, it can be used to separate a metal ion or a metal ion complex from an aqueous solution. A suitable immiscible liquid organic solvent extractant, which usually includes a diluent such as kerosene and/or fuel oil, is mixed with the solution and the metal ion or metal ion complex is dissolved, or pulled into the organic solvent extractant by a chemical bonding, to form an immiscible organic phase. The resulting emulsion or dispersion is transferred to a settler in which a lack of agitation promotes gravity settling for disengaging the organic and aqueous phases. The "loaded" organic phase containing the extracted metal ion or metal ion complex is transferred to a stripper where the extracted metal or metal ion complex is stripped from the organic phase and the organic solvent extractant is recycled for another extraction.
In conventional solvent extraction processes, separation of the organic phase after mixing is slow and does not always yield a clean separation. That is, some of the organic phase, which can be in the form of small droplets, remains in the aqueous phase even after long settling periods. Centrifuging to accelerate and enhance the degree separation is not practical for industrial operations.
Many techniques have been used to magnetize non-magnetic materials to permit these to be selectively separated from a mixture by magnetic separation.
For example, U.S. Pat. No. 3,926,789 (Shubert) discloses selectively coating the surface of one or more components in a mixture with a magnetic fluid consisting of a suspension of magnetic particles in a liquid carrier and then subjecting the mixture to a magnetic separation.
J. Y. Hwang, et al., Society of Mininq Engineers of AIME preprint No. 85-11, presentation at SME-AIME Annual Meeting Feb. 24-28, 1985 discloses a separation process including the steps of admixing a flocculant and particles of magnetite with a slurry containing finely-ground alunite ore to co-flocculate the magnetite and quartz liberated from the ore and separating the co-flocculant from the alunite in a high gradient separator.
P. Parsonage, "Selective Magnetic Coating for Mineral Separation", Trans. Instn. Min. Metall, 93, March 1984, discloses selectively coating mineral and metallic particles with colloidal magnetite and then separating thus-coated particles with a magnetic separator.
U.S. Pat. No. 4,834,898 (Hwang) discloses a reagent for magnetizing particles of a nonmagnetic material consisting of particles of a magnetic material, such as magnetite, coated with two layers of surfactants and dispersed in water.
None of these references discloses, and applicant is unaware of any other prior art which, discloses magnetizing an organic solvent extractant so that the separation of an organic phase, containing the extractant and one or more extracted components, from an aqueous mixture can be enhanced by magnetic separation.